Esters of diacyl-glycerophosphoric acids



Patented Aug. 24, 1948 UNITED STATES PATENT OFFICE 2,447,715 ESTERS OFDIACYL-GLYCEROPHO SPHORIC ACIDS William Gordon Rose, Berkeley, Califassignor to the United States of America as represented by the Secretaryof Agriculture No Drawing. Application June 12, 1947, Serial No. 754,257

13 China.

(Granted under the act of March a, 1883, as

amended April 30,

More particularly, the invention relates to thepreparation of aminoethylesters of dlacyl-glycerophosphoric acids wherein the acyl groups arealiphatic and contain at least eight carbon atoms. These compounds maybe illustrated by the following formulae:

(Aminoethyl ester of alpha, gamma-diacyl-glycerophosphoric acid)(Aminoethyl ester of alpha, beta-diacyl-glycerophoa' phoric acid)wherein represents an aliphatic acyl radical containing at least 8carbon atoms.

Cephalin is a naturallyoccurring mixture 0! aminoethyl esters ofdiacyl-glycerophosphoric acids. Thus, these esters can also be namedwith respect to their relationship to cephalin. For instance, thefollowing compound can be named the amlnoethyl ester of alpha,gamma-dipal:

5 mitoglycerophosphoric acid or alpha, gammadipalmitocephalin:

and the following compound can be named the aminoethyl ester of alpha,gamma-distearoglycerophosphoric acid or alpha, gamma-distearocephalin.

This invention relates with further particularity to the preparation ofnovel compounds, namely, phthalimidoethyl esters ofdiacyl-glycerophosphoric acids wherein the acyl groups are aliphatic andcontain at least eight carbon atoms. These compounds may be illustratedby the formulae:

(Phthalimidoethyl ester of alpha, gamma-diacyl-glycerophosphoric acid)(Phthalimidoethyl ester of alpha, beta-diacyl-glycerophosphoric acid)wherein represents an aliphatic acyl radical containing at least 8carbon atoms.

These novel compounds can also be named with respect to'theirrelationship to cephalin. Thus, for instance, the phthalimidoethyl esterof alpha, gamma-dipalmitoglycerophosphoric acid can be referred to asalpha, gamma-dipalmitophthalylcephalin.

Accordingly, an object of this invention is to prepare aminoethyl estersof diacyl-glycerophosphoric acids wherein the acyl groups are allphaticand contain at least eight carbon atoms.

Another object of this invention is to prepare phthalimidoethyl estersof diacyl-glycerophosphoric acids wherein the acyl groups are aliphaticand contain at least eight carbon atoms.

A further object of this invention is to provide novel compounds,namely, phthalimidoethyl esphoric acid amide instead of the desiredester.

Another method involves the heating together of brometbylamine picrateand the monosilver salt of dipalmitoglycerophosphoric acid. Thisprocedure gives very poor yields probably due to formation of piperazlnederivatives.

I have found that the aminoethyl esters can be obtained in good yield bythe reaction of a diacylglycerophosphoryl chloride withbeta-hydroxyethylphthalimide. The resulting compound, phthalimidoethylester of diacyl-glyceromonochlorophosphoric acid, is subjected to alimited hydrolysis to remove the chlorine atom attached to thephosphorus atom whereby the phthalimidoethyl ester of thediacyl-glycerophosphoric acid is produced. This material is then cleavedby reaction under refluxing conditions with hydrazine, hydrazinehydrate, or the mineral acid salts of hydrazine to produce theaminoethyl ester of the diacyl-glycerophosphorlc acid. The reactions canbe demonstrated by the following equations:

o mo -o- -a The following example, which describes the (A) Preparationof alpha, gamma-dipalmitophthalylcephalin Phosphorus oxychloride in thequantity of 9.18 grams was placed in a two-necked flask with 30 ml. oildry pyridine and 40 ml. of chloroform. The flask was provided with anagitator adapted to scrape the bottom of the flask and was surrounded bya water bath at 10-15 C. The agitator was started and then 34.2 grams ofalpha, gamma-dipalmitin in 200 ml. of alcohol-free chloroform was addedduring the course of 1 hour. The solution was stirred at 25 C. for 30minutes, then at 30-35 C. for 30 minutes, then cooled to 10-15 C. again,and 11.45 grams betahydroxyethylphthalimide in 200 m1. chloroform addedduring the course of 1 hour. The solution was then stirred at 25 C. for30 minutes and at 30-35 C. for 30 minutes to complete the reaction.After cooling to 28 C., 1.15 ml. of water in 4 ml. pyridine was added.This step causes the hydrolysis of the chlorine atom. Most of the aid ofether, and was shaken moderately. The

emulsified aqueous layer was withdrawn, acidified, and'the ether thatseparated added to the main ether solution. The ether layer was washedwith dilute hydrochloric acid and with water and was then filteredthrough a thick soft paper or through cotton and left overnight at C.

Filtration removed 3.4 grams of material that melted at -50-60 C., butdid not become-clear until 160 C. To obtain the principal reaction- 1product, the filtratewas next left for 5 hours at -18 C. and filtered atthis temperature. The precipitate retained much ether and was airdriedovernight, as it melted in the retained solvent when it was dried in avacuum desiccator without preliminary air drying. The dried productweighed 39.5 grams and melted at 43-46 C. It was found later to belargely phthalylcephalin, but contained several other substances.

The crude material was purified by dissolving it in 600 ml. of hothexane, filtered hot and allowed to stand 18 hours at room temperature.Filtration gave 4.8 grams of impure phthalylcephalin that sintered at 63C. and melted from 70-76 C. This was dissolved in 50 ml. of methanol,filtered hot and allowed to stand at room temperature overnight.Filtration gave 3.0 grams of crystals of phthalylceph'alin that sinteredat 64 C. and melted at 67-68 C. The hexane filtrate (above) containedstill more phthalylcephalin. It was concentrated to 200 ml., seeded withsome of the crystals from the methanol crystallization and thereupondeposited more crystals when allowed to stand at room temperature for 3hours with occasional stirring. Filtration gave 14.7 grams that sinteredat 60 C. and melted at 64-73 C. This product was dissolved in 150 ml. ofhot methanol and the hot solution was filtered through cotton andallowed to stand for 16 hours at room temperature. Filtration gave 12.5grams that sintered at 69 C. and melted at 70-72 C. The two productsthat had been recrystallized from methanol were combined andrecrystallized from 200 ml. of hexane,

the solution being filtered after standing 1 hour at room temperature.The yield was 13.25 grams of product (alpha,gamma-dipalmitophthalylceph'alin or phthalimidoethyl ester of alpha,gamma-dipalmitoglycerophosphoric acid) that melted at 71-72 C.

Analysis: Calcd. for C45H'1sOioNP: N, 1.70; P, 3.77; C, 65.74; H, 9.32;equiv, wt. 822.1. Found:

N, 1.66; P, 3.85; C, 66.09; H, 9.47; equiv. wt. 825.

(B) Preparation of alpha, gamma-dipalmitocephalin Four andeleven-hundredths grams of phthalylcephalin prepared as described abovewas dissolved in 100 ml. of hot neutral monomethyl ether of glycol andneutralized by the addition of 10 4 ml. of 0.5 N N aOH. Hydrazinehydrate in monolln was accomplished by taking advantage of theunexpected property that it is insoluble in ether but is very readilysuspended therein. The water suspension was transferred to a separator-yfunnel with 300 ml. of ether, shaken and the aqueous layer removed. Theether layer and the solid that collected at the ether-water interfacewere washed with water until the washings were neutral; The ethercontaining the suspended solid was then filtered, washed with ether anddried. The dry residue amounted to 2.9 grams and melted at 178-200 C.Recrystallization from 190 ml. absolute alcohol gave 2.47 grams thatsintered at 187 C. and melted with decomposition at 192-193 C.,depending on the rate of heating. Further recrystallization from alcoholdid not alter the melting point. The product was alpha,gamma-dipalmitocephalin or aminoethyl ester of alpha,gamma-dipalmitoglycerophosphoric acid.

Analysis: Calcd. for alpha, gamma-dipalmitocephalin, CmI-I'uOsNP: N,2.02; P, 4.48; C, 64.22; H, 10.78 percent; equiv. wt. 692.0. Found: N(Dumas), 2.07; Amino N (Van Slyke in acetic acid), 1.86; P, 4.50; C,63.75; H, 10.52 percent;

equiv. wt. (titration in neutral alcohol), 689.

It was necessary to add vanadium pentoxide t0 the substance, asdescribed for phosphoric acid esters by Wagner-Jauregg and Griesshaber(Berichte Deut. Chem. Geseil, vol. 70, p, 1458 (1937) to obtain correctcarbon analyses. Combustion of the substance alone, or with copper oxide gave carbon values that were 2 to 3 percent As set forth above thefirst step in the process involves the reaction ofbeta-hydroxyethylphthalimide with a diacyl-glycerophosphoryl chloride.As the latter reactant, many different compounds can be used wherein theacyl radicals are aliphatic and contain at least eight carbon atoms. Theacyl radicals can be attached at the alpha and gamma positions of theglycerine nucleus, in which case the phosphoryl chloride group is at thebeta position; or, the acyl groups can be attached at the alpha and betapositions, in which case the phosphoryl chloride group is attached atthe gamma position.

These diacyl-glycerophosphoryl chlorides are most conveniently preparedby reacting a diacyl ester of glycerine with phosphorus oxychloride. Forexample, by reacting alpha, gamma-dipalmitin with phosphorus oxychloridein the presence of pyridine, alpha, gamma-dipolmitoglycerophosphorylchloride can be prepared. Thus, one can employ as thediacyl-glycerophosphoryl chloride reactant the phosphorus oxychloridereaction product with any of the following diacyl esters of glycerine,i, e.', alpha, gamma-dicaprylin; alpha, beta-dicaprylin; alpha,gamma-dipelargonic ester of glycerine; alpha, beta-dipelargonic ester ofglycerine; alpha, gamma-dicaprin; alpha, beta-dicaprin; alpha,gamma-diundecylic ester of glycerine; alpha, beta-diundecylic ester ofglycerine; alpha, gamma-dilaurin; alpha, betadilaurin; alpha,gamma-ditridecylic ester of glycerine; alpha, beta-ditridecylic ester ofglycerine;

alpha, gamma-dimyristin; alpha, beta-dimyristin;

alpha, gamma-dipentadecylic ester of glycerine; alpha,beta-dipentadecylic ester of glycerine; alpha, gamma-dipalmitin; alpha,beta-dipalmitin; alpha, gamma-dimargarin; alpha, beta-dimergarin; alpha,gamma-distearin; alpha, beta-distearin; alpha, gamma-dinondecylic esterof glycerine; alpha, beta-dlnondecylic ester of glycerine; alpha,gamma-diarachadin; alpha, beta- V insure complete reaction.

diarachadin; alpha,gamma-dlolein; alpha. beta-.-

. iolein; alpha, gamma-dielaidin; alpha, beta-dielaidin; alpha,gamma-dipalmitolein; alpha. betadipalmitolein; alpha, gamma-dilinolein;alpha, beta-dilinolein; and so forth.

Further, it is possible to use glycerine esters wherein the two acylgroups are dissimilar, for instance-alpha-stearic, beta-palmitic esterof glycerine; alpha-lauric. gamma-palmitic ester of glycerine:alpha-stearic, gamma-oleic ester of glycerine; alpha-palmitic,gamma-linoleic ester of glycerine; and so forth.

Further, if it is not desired to prepare an individuual final compoundbut mixtures, one can employ mixtures of different diesters ofglycerine. For instance. one could employ the mixtures of diglyceridesformed by heating glycerlne and a catalyst with a triglyceride. Thus,mixtures of digiycerides suitable for use in the process could beprepared by heating glycerine with a catalyst and with coconut oil,palm-kernel oil, olive oil, taliow. suet, cottonseed oil, peanut oil,lard, olive oil,-whale oil, sardine oil. corn oil, soybean oil, and soforth. Mixtures of diglycerides can also be prepared by reacting anexcess of giycerine, in

' ed to 59.2 grams of phthalic anhydride, and after the initial heat ofreaction had subsided, the mixture was heated at 150 C. for 30 minutes.It was then allowed to cool to about 90 C. and poured into-800 ml. ofwater. The crystals so obtained were chilled in ice and filtered, giving46.7 grams of beta-hydroxyethylphthalimide,

Analysis: Calcd. for CioHeOaN: C. 62.82; H, 4.74; N, 7.33. Found: C,62.81; H, 4.65; N. 7.40.

In the reaction of the diacyl glycerine ester with phosphorusoxychloride to prepare the diacyl-glycerophosphoryl chloride, it isnecessary to add a hydrogen chloride acceptor to the reaction mixture.For this purpose, pyridine, quinoline, dimethyl aniline or othertertiary amines are suitable. The temperature of the reaction should bekept low. It has been found that temperatures from about to about 35 C.are suitable. Preferably, the reaction should be conducted at the lowertemperature, about 10-45 C., and then heating toabout 30-35 C. for ashort time to The diacyi-glycerine ester and phosphorus oxychlorideshould be employed in approximately equimolar proportions. It ispreferable to employ a solvent in this reaction. Organic solvents suchas chloroform, di-

chloromethane, benzene and so forth are suitable. Any other inert liquidwhich will dissolve the diacyl-glycerine ester-phosphorus oxychloridecomplex and the tertiary amine hydrochloride can be used.

ride with the beta-hydroxyethylphthalimide, it is necessary I to employa hydrogen chloride acceptor (quinoline, pyridine, diemethylaniline, orother tertiary amine). It has been found to be convenient to add anexcess of the hydrogen chloride acceptor in the first reaction(diacylglycerine ester and phosphorus oxychloride) whereby sufliclentacceptor will remain in the reaction mixture for the second reaction(diacylglycerophosphorylchloride and beta-hydro ethylphthalimide). Inregard to the latter reaction. the same temperature, proportions, and

solvents are applicable as to the former reaction.

In the hydrolysis step involving the removal of the chlorine atom fromthe complex phthalimidoethyl ester of diacylglyceromonochlorophosphoricacid. the amount of water is not critical. At least an equimolarproportion of water I should be added but an excess will not bedisadvantageous. The temperature during-this step should be kept atabout 25 C, or less to prevent hydrolysis of the ester linkages. Nosolvent is necessary in the hydrolysis, but a solvent such as pyridinecan be used if desired to assist in transfer of the water to themixture.

The expression limited hydrolysis," as used herein, means a controlledhydrolysis whereby only the chlorine atom on the phosphorus atom ishydrolyzed and the ester linkages are not affected. h I t In thecleavage step, hydrazine is heated with the phthalylcephalin. One mol ofthe phthalylcephalin requires 1 to 2 mols of hydrazine. In this cleavagestep, the hydrazine can be replaced by hydrazine hydrate, hydrazinehydrochloride, hydrazine sulphate, or other hydrazine mineral acidsalts. It is preferable to use a solvent; monomethyl glycol ether,monoethyl glycol ether, ethanol and methanol are suitable. The reactantsare preferably refluxed to bring about the reaction and to prevent lossof solvent and/or hydrazine.

The aminoethyl'esters produced according to the described process can beused to replace lecithin in a variety of pharmaceutical preparations andcosmetics where they are useful as emulsifying and skin-softeningagents. These products are also useful as antiblushing agents inchocolates and as water-binding and dispersing agents in oleomargarine.Because of their surface-active properties, the aminoethyl esters arealso useful in preparing oil-in-water emulsions of insecticldes andfungicides and in promoting the reaction of hydrophilic materials withhy--v drophobic materials.

are useful as a convenient source for the preparation of thecorresponding aminoethyl esters. The phthalimidoethyl esters are quitestable and can be kept for; long periods contrary to the amimethylesters. The former can be readily cleaved with hydrazine when aminoethylesters are required. The phthalimidoethyl esters are generally useful asintermediates from whichto prepare many different glycerophosphoric acidderivatives. I

The foregoing example indicates methods of purifying the product andintermediates. These steps can, of course, be omitted if it is notdesired to obtain a chemically pure grade of material.

In a copending application, Serial No. 754,256,

' filed June 12, 1947, now U. S. Patent 2,436,699, I

have disclosed a method of preparing aminoethyl esters ofdiacyl-glycerophosphoric acids involving reaction ofcarbobenzoxyaminoethanol with a diacyl-glycerophosphoryl chloride,followed by 9 limited hydrolysis, and cleavage with phosphonium iodide.Having thus described the invention, what is claimed is:

1. A process comprising reacting a diacyi-glycerophosphoryl chloride,wherein the acyl radicalsare aliphatic and contain at least 8 carbonatoms, with beta-hydroxyethylphthalimide in the presence of a tertiaryamine at a temperature of about from 10 C. to '5" C., subjecting theresulting phthallmidoethyl ester of diacyl-glyceromonochlorophosphoricacid to limited hydrolysis by reaction with water at a temperature notexceeding about 25 C. to form the phthalimidoethyl ester ofdiacyl-glycerophosphoric acid, and refluxing this last-formed ester witha member selected from the group consisting of hydrazine, hydrazinehydrate, and the mineral acid salts of hydrazine to produce anaminoethyl ester of a diacyl-giyeerophosphorlc acid.

2. A process comprising reacting a diacylglycercphosphoryl chloride,wherein the acyl radicals are aliphatic and contain at least 8 carbonatoms, with beta-hydroxyethylphthalimide in the presence oi a tertiaryamine at a temperature of about from 10 C. to 35 C., subjecting theresulting phthalimidoethyl ester of diacylglyceromonochlorophosphoricacid to limited hydrolysis by reaction with water at a temperature notexceeding about 25 C. to form the phthalimidoethyl ester ofdiacyl-glycerophosphoric acid, and refluxing this last-formed ester withhydrazine hydrate to produce an aminoethyl ester of adiacyl-glycerophosphoric acid.

3. A process comprising reacting an alpha, gamma-diacylglycerophosphorylchloride, wherein the acyl radicals are aliphatic and contain at least 8carbon atoms, with'beta-hydroxyethylphthalimide in the presence or atertiary amine at a temperature of about from 10 C. to 35 C., subjectingthe resulting phthalimidoethyl ester of a l p h a, gammadiacylglyceromonochlorophosphoric acid to limited hydrolysis by reactionwith water at a temperature not exceeding about 25 C. to form thephthalimidoethyl ester of alpha, gamma-diacylglycerophosphoric acid, andrefluxing this last-formed ester with a member selected from the groupconsisting of hydrazine, hydrazine hydrate, and the mineral acid saltsof hydrazine to produce the aminoethyl ester of an alpha,gamma-diacylglycerophosphoric acid.

4. A process comprising reacting alpha. Eamma-dipalmitoglycerophosphoryl chloride with beta-hydroxyethylphthalimidein the presence of.

l0 sisting of hydrazine, hydrazine hydrate, and the mineral acid saltsof hydrazine to produce the aminoethyl ester of alpha,gamma-dipalmitoglycerophosphoric acid.

5. The process of claim 1 wherein the tertiary amine is pyridine.

6. A process comprising reacting a diacylglycerophosphoryl chloride,wherein the acyl radicals are aliphatic and contain at least 8 carbonatoms, with beta-hydroxyethylphthalimide in the presence of a tertiaryamine at a temperature of about from 10 C. to 35 C. and subjecting theresulting phthalimidoethyl ester of diacyl-glyceromonochiorophosphoricacid to limited hydrolysis by reaction with water at a temperature notexceeding about 25 C. to form the phthallmidoethyl ester ofdiacyl-glycerophosphoric acid.

7. A process comprising reacting an alpha, gamma diacylglycerophosphoryl c h 1 o rid e, wherein the acyl radicals are aliphaticanacontain at least 8 carbon atoms, with beta-hydroxyethylphthalimide inthe presence of a tertiary amine at a temperature of about from 10 C. to35 C. and subjecting the resulting phthalimidoethyl ester of alpha,gamma-diacyl-giyceromonochlorophosphoric acid to limited hydrolysis byreaction with water at a temperature not exceeding about 25 C. to formthe phthalimidoethyl ester of alpha, gamma-diacyl-glycerophosphoricacid.

8. A process comprising reacting alpha, gamma dipalmitoglycerophosphorylchloride with beta-hydroxyethylphthalimide in the presence of a tertiaryamine at a temperature or about from 10 C. to 35 C. and subjecting theresulting phthalirnidoethyl ester of alpha,gamma-dipalmitogiyceromonochlorophosphoric acid to limited hydrolysis byreaction with water at a tempera.- ture not exceeding about 25 C. toform the phthalimidoethyl ester of alpha,gamma-dipalmitoglycerophosphorlc acid.

9. The process or claim 6 wherein the tertiary amine is pyridine.

10. A phthalimidoethyl ester or a diacyl-glycerophosphoric acid whereinthe acyl radicals are aliphatic and contain at least 8 carbon atoms.

11. A phthalimidoethyl ester of an alpha, gamma-diacylglycerophosphorlcacid wherein the acyl radicals are aliphatic and contain at least 8carbon atoms.

12. Phthalimidoethyl ester of dipalmitoglycerophosphoric acid.

v13. Phthalimidoethyl ester of alpha, gammadipalmitoglycerophosnhoricacid. 4

WILLIAM GORDON ROSE.

.REFERENCES CITED The following references are of record in the file ofthis patent:

Sidgwick, "Organic Chemistry oi Nitrogen," new edition, 1937, OxfordUniversity Press (London), pages 14 and 15.

